The ocean holds about 97 percent of the Earth's water; the remaining three percent is found in glaciers and ice, below the ground, in rivers and lakes. Of the world's total water supply of about 332 million cubic miles of water, about 97 percent is found in the ocean.

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The student adds 6 m nh3 to be cuso4 solution until the cu2+ ion is essentially all converted to cu(nh3)42+ ion. the voltage of

Gnoma [55]

Here we have to get the residual concentration of Cu²⁺ in the reaction.

The residual concentration of [Cu²⁺] is 2.137×10⁸ m

The reaction between ammonia (NH₃) and CuSO₄ in ionic form is - Cu²⁺ + 4 NH₃ = [Cu(NH₃)₄]²⁺.

Thus 1 mole of Cu²⁺ will react with 4 moles of NH₃.

Now 6m NH₃ or 6 moles of ammonia will react with $\frac{6}{4}$ = 1.5 moles of Cu²⁺.

Thus the Nernst equation of the reaction is $E_{Cell}$ = E° + $\frac{0.059}{n}$ log $\frac{Cu^{2+} }{Cu}$ .

Here the number of moles is 3, as 6 moles of ammonia will react with 1.5 moles of cu²⁺. and the standard reduction potential (E°) of Cu²⁺/Cu system is (+) 0.674V and the cell potential is 0.92V

On plugging the values in the equation, we get,

0.92 = 0.674 + $\frac{0.059}{2}$ log[Cu²⁺]

Or, 0.029 log [Cu²⁺]= 0.246

Or, log [Cu²⁺] = 8.33

Or, [Cu²⁺] = 2.137×10⁸

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